The mitral valve connects the left atrium to the left ventricle and regulates blood flow between the two heart chambers. In the healthy heart, as the left atrium contracts, the mitral valve opens to let blood flow from the left atrium into the left ventricle. Then, when the left ventricle contracts to force blood throughout the body, the mitral valve closes to prevent blood from flowing back into the atrium. The valve has two flaps, or leaflets, that coapt to close the valve.
Mitral regurgitation, or mitral insufficiency, refers to the mitral valve's failure to close sufficiently, thereby allowing excessive leakage of blood from the ventricle back into the atrium. Ischemic mitral regurgitation is a type of mitral regurgitation caused by acute myocardial infarction and the left ventricular remodeling that can eventually result from the infarction. Millions of people throughout the world suffer from ischemic mitral regurgitation, including many who also suffer from chronic heart failure. In most patients with ischemic mitral regurgitation, the valve itself is structurally normal.
In end-stage heart failure patients, the mechanism of mitral regurgitation is multifactorial and is related to changes in left ventricular geometry, with a subsequent displacement of the subvalvular apparatus, annular dilatation, and restrictive leaflet motion, which ends in failure of the leaflet coaptation. Physiologically, ischemic mitral regurgitation in these patients will lead to left ventricular overload and decrease of stroke volume. This takes place at first in response to exercise and later can occur even at rest, which can activate systemic and local neurohormonal systems and cytokines that deteriorate cardiac loading conditions, promoting left ventricular remodeling and dysfunction. This may generate a vicious cycle where regurgitation produces more regurgitation.
Mitral valve repair may interrupt this cycle to safely improve clinical outcomes. The use of stringent restrictive rings (i.e., rings that are smaller than the measured size of the valve annulus) in valve annuloplasty may lead to better leaflet coaptation, which, in turn, decreases regurgitation and promotes reverse remodeling. The undersizing of the mitral annulus can lead to acute geometric changes of the base of the left ventricle, which may diminish left ventricular volume and wall stress.